Components of the cytotoxic T lymphocyte membrane are intimately involved in the mechanism of lymphocyte-mediated cytotoxicity. Many cell surface glycoproteins contain a unique terminal carbohydrate residue, sialic acid. Enzymatic removal of the sialic acid results in an enhancement of the cytolytic capacity of the lymphocytes. I will examine the thesis that this enhancement is due to the loss of the carboxyl group of the sialic acid. Other aspects of this study include the detection of those glycoproteins which are expressed only after differentiation of small lymphocytes into cytotoxic lymphocytes and conversely, those which are no longer expressed after differentiation. Further, an identification of the T cell receptor and other surface proteins involved in target cell cytolysis will be attempted by limited proteolysis.